Journal of Autism and Developmental Disorders (Ó 2006)
DOI 10.1007/s10803-006-0093-2
Adaptive and Maladaptive Behavior in Children
with Smith-Magenis Syndrome
Staci C. Martin,1,2,5 Pamela L. Wolters,1,2 and Ann C. M. Smith3,4
Children with Smith-Magenis Syndrome (SMS) exhibit deficits in adaptive behavior but
systematic studies using objective measures are lacking. This descriptive study assessed
adaptive functioning in 19 children with SMS using the Vineland Adaptive Behavior Scales
(VABS). Maladaptive behavior was examined through parent questionnaires and the
Childhood Autism Rating Scale. Cognitive functioning was evaluated with an age-appropriate
test. Children scored below average on VABS Communication, Daily Living Skills, and
Socialization scales. Learning problems and hyperactivity scales on the Conner’s Parent
Rating Scale were elevated, and girls were more impulsive than boys. Stereotypic and selfinjurious behaviors were present in all children. Cognitive functioning was delayed and
consistent with communication and daily living skills, while socialization scores were higher
than IQ.
KEY WORDS: Smith-Magenis syndrome; adaptive functioning; social skills; IQ.
Smith-Magenis Syndrome (SMS) is a congenital
disorder associated with an interstitial deletion on
chromosome 17 (17p11.2), which is related to a
specific pattern of physical, behavioral, and developmental characteristics. This syndrome is estimated to
be present in 1 in 25,000 children (Greenberg et al.,
1991), and is likely under-diagnosed due to an
overlap of symptoms with other developmental
disorders and a lack of awareness of the disorder in
much of the medical community (Smith & Gropman,
2001).
1
2
3
4
5
HIV and AIDS Malignancy Branch, National Cancer Institute,
Bethesda, MD, USA.
Medical Illness Counseling Center, Chevy Chase, MD, USA.
Medical Genetics Branch, National Human Genetics Research
Institute, Bethesda, MD, USA.
Georgetown University Medical Center, Washington, DC, USA.
Correspondence should be addressed to: Staci C. Martin,
National Cancer Institute, 9030 Old Georgetown Road, 107,
Bethesda, MD 20892-8200, USA; E-mail: [email protected]
Initially described by Smith et al. (Smith et al.,
1986; Smith, McGovran, Waldstein, & Robinson,
1982), the syndrome was delineated more fully in
later publications that define the complex phenotype
(Greenberg et al., 1991, 1996; Potocki, Shaw, Stankiewicz, & Lupski, 2003; Smith & Gropman, 2001).
Unique physical characteristics seen in children with
SMS include craniofacial anomalies, such as brachycephaly with a flat mid-face, a broad nasal bridge,
deep-set eyes, a down-turned mouth, a prominent
jaw, short fingers, and short stature (Greenberg et al.,
1991; Potocki et al., 2003). An increased risk of
certain health conditions, including opthalmological
and otolaryngologic problems, cardiac and/or renal/
urinary tract abnormalities, and hypercholesterolemia, has been reported as well. Recent data suggest
that deletion size does not correlate with the major
clinical features of SMS and that the clinical spectrum remains variable even among individuals with
the same size (common) deletion (Potocki et al.,
2003).
Ó 2006 Springer ScienceþBusiness Media, Inc.
Martin, Wolters, and Smith
A distinct and complex neurobehavioral phenotype has been described in SMS that includes
cognitive impairments, stereotypies, maladaptive
behaviors, and a chronic sleep disturbance that is
associated with an unusual inverted circadian rhythm
of melatonin (De Leersnyder et al., 2001; Smith,
Dykens, & Greenberg, 1998a, 1998b). Deficits in
adaptive behavior typically become apparent in late
infancy or early childhood and seem to last throughout the lifespan, with a vast majority of adults with
SMS being unable to fully care for themselves. One
study of adaptive functioning among adults with
SMS reported that all participants required some
level of supervision; more than half lived with their
parents, and the rest lived in residential facilities
(Udwin, Webber, & Horn, 2001). Among children,
poor adaptive functioning has been described qualitatively, but published objective measurements
describing clearly defined patient groups are lacking.
A study combining data from teenagers and adults
ages 14 to 51 found significant delays in each of the
three primary domains of adaptive functioning
(Communication, Daily Living Skills, Socialization)
as measured by the Vineland Adaptive Behavior
Scales (VABS; Dykens, Finucane, & Gayley, 1997).
In addition to delays in the acquisition of
adaptive skills, studies suggest that significant behavior problems are common, including temper
tantrums, self-injurious behaviors (SIBs), and physical aggression towards others (Greenberg et al.,
1991). These behavioral difficulties often are significant enough to interfere at least moderately with
daily functioning (Finucane, Dirrigl, & Simon, 2001)
and sometimes warrant professional intervention. In
a small study that examined maladaptive behavior in
10 individuals with SMS (mean age=27 years, age
range 14–51), 80% of the sample was described as
‘‘impulsive’’ and ‘‘overactive’’ on the Reiss Screen for
Maladaptive Behavior (Dykens et al., 1997).
Finucane et al. (2001) described patterns of selfinjurious behavior among 15 children with SMS
(mean age=6.5 years). Responses to questionnaires
administered to parents over the telephone indicated
that 87% of the children engaged in hand or wrist
biting, and one-fourth to one-half engaged in head
banging, hair pulling, and skin picking. Interestingly,
some children with SMS engage in head banging or
rocking behaviors while falling asleep (Smith et al.,
1998a).
Some evidence suggests that behavior problems
in children with SMS are more severe than those seen
in several other genetically disordered populations.
For example, Dykens and Smith (1998) compared
groups of children with SMS, Prader-Willi Syndrome, and nonspecific intellectual disabilities. Their
results showed that the children with Smith-Magenis
Syndrome scored significantly higher than the other
two groups on a measure of externalizing behavior
problems (Child Behavior Checklist; Achenbach &
Edelbrock, 1983). In another paper comparing maladaptive behavior among individuals with PraderWilli, Cri du chat, and Smith-Magenis Syndromes, it
was found that individuals with SMS scored higher
on scales assessing irritability/agitation and hyperactivity/noncompliance (Clarke & Boer, 1998). These
results should be interpreted with caution, however,
as no statistical analyses regarding the significance of
the findings were reported.
From the available research, some degree of
cognitive deficits is invariably present among individuals with SMS. Reports estimate that as many as
three-fourths of children with SMS exhibit moderate
to severe mental retardation (Udwin et al., 2001).
Also, it is important to note that significant expressive language delays in early childhood in the
presence of maladaptive behaviors can impact reliable cognitive and functional assessment in this
syndrome (Gropman, Wolters, Solomon, & Smith,
1999; Smith & Gropman, 2001).
Because of the limited research on cognitive and
adaptive functioning in children with SMS, it is helpful
to examine what is known about these variables in
other developmentally delayed populations. In autistic
children, for example, both cognitive and adaptive
deficits have been well-documented (Freeman, Ritvo,
Yokota, Childs, & Pollard, 1988). Studies have put
forth a systematic relationship between cognitive and
adaptive functioning in autistic children, with adaptive
skills often more impaired than intellectual abilities
(Freeman et al., 1991). It also has been noted that
cognitive functioning is unrelated to the number of
maladaptive behaviors reported by parents of children
with autism (Freeman et al., 1991).
Among children with Asperger’s Syndrome
(AS), results of several studies have documented
cognitive functioning in the normal range, while
socialization and daily living skills are described as
significantly below average (Szatmari, Archer,
Fisman, Streiner, & Wilson, 1995). By contrast,
children with Williams Syndrome present with significant impairments in both cognitive and adaptive
skills (Greer, Brown, Pai, Choudry, & Klein, 1997).
Relative to other developmentally delayed populations, the proportion of moderate to severe mental
Behavior in Smith-Magenis Syndrome
retardation among individuals with SMS was higher
than for individuals with Prader-Willi Syndrome, and
was similar to individuals with Cri du chat Syndrome
(Clarke & Boer, 1998). Estimates of impairment were
obtained via caregiver report in this study.
Findings from some other developmentally
delayed populations have suggested the presence of
age and gender differences in behavioral and/or
cognitive functioning. For example, autistic boys have
been described as higher functioning on measures of
receptive vocabulary and visual-motor integration,
and have been rated as less socially competent with
more stereotypic play behavior than girls (Lord,
Schopler, & Revicki, 1982; McLennan, Lord, &
Schopler, 1993). Differences in cognitive and adaptive
functioning between boys and girls and children of
various ages are areas that have not been extensively
studied in the SMS population. Among the few studies
that have addressed this topic, Dykens and Smith
(1998) found no significant age- or gender-related
associations with the number of stereotypic and selfinjurious behaviors or level of cognitive delay.
Another study found a higher rate of self-injurious
behavior in older children with SMS compared with
younger children (Finucane et al., 2001).
Clearly, findings from studies of various developmentally delayed populations indicate that patterns of cognitive and adaptive functioning differ
with respect to profiles of strengths and weaknesses
and the relationship between these variables. While
little is known about the specific pattern of deficits
among children with SMS, available descriptions of
cognitive and adaptive functioning clearly suggest
that these are areas of concern in the families’ lives.
However, several studies in this topic area combine
data from children, adolescents, and adults with
SMS, thus obscuring the picture of adaptive functioning in each age group. Other studies describe
adaptive functioning in this population without the
use of a standardized, validated assessment instrument.
The first goal of this study is to describe the
adaptive and maladaptive behavior patterns among
children with SMS using reliable, objective assessment tools. The second goal is to examine the
relationship between cognitive functioning and adaptive and maladaptive behavior. Since little is known
about possible gender or age differences in the SMS
population, exploratory analyses were conducted in
order to assess for systematic differences based on
gender and/or age with respect to the variables of
interest.
METHOD
Participants
Children throughout the United States with a
confirmed diagnosis of Smith-Magenis Syndrome
were eligible to participate in this research study
conducted at the National Institutes of Health (NIH)
in Bethesda, Maryland. Diagnoses of SMS were
confirmed through molecular cytogenetic testing that
included fluorescent in situ hybridization (FISH).
Participants were consecutively enrolled on an IRBapproved natural history protocol of SMS at the
NIH (01-HG-0109) between 1998 and 2003. Parental
informed consent was obtained prior to enrollment.
The total sample consisted of 19 children, 10
girls and 9 boys, between the ages of 2 and 12 years
(mean age 5.7 years). All were Caucasian, and all
were the biological offspring of their current caregivers. The mean level of parental education was
15.7 years, and there was no difference between
parents of boys and girls with respect to years of
education (ns). Also, girls and boys did not differ
with respect to mean age (ns).
Measures
Cognitive Functioning
Child participants were administered a test of
cognitive functioning, either the Bayley Scales of
Infant Development – Second Edition (BSID-II;
Bayley, 1993), or the Stanford Binet Intelligence
Scale – Fourth Edition (SB-IV; Thorndike, Hagen, &
Sattler, 1986), depending on their age and ability
level. The BSID-II is a developmental measure of
cognitive functioning administered to infants and
young children up to the age of 42 months. It
provides a Mental Developmental Index that is
comparable to an IQ score, and has a mean of 100
and standard deviation of 15. Reliability and validity
of the BSID-II have been established through numerous studies (Atkinson, 1990). The SB-IV is a widely
used measure of cognitive abilities given to individuals between the ages of 2 years, 6 months to
23 years, 11 months. The child’s performance on
individual subtests yields standard scores on several
subscales and a Composite Standard Age Score
(SAS) with a mean of 100 and standard deviation
of 16. Psychometric properties of the SB-IV are well
established (Dacey, Nelson, & Stoeckel, 1999). Three
children who were older than the upper age limit for
the BSID-II were unable to obtain basal scores on the
Martin, Wolters, and Smith
SB-IV. For these children, the BSID-II was administered and a ratio IQ was computed. Ratio IQ
computations from the BSID-II have been shown to
be a reliable indicator of performance on the SB-IV
(Atkinson, 1990; Lindsey & Brouwers, 1999). Thus,
use of this method in our study was not expected to
impact our findings.
Adaptive Behavior
Parents were interviewed with the Vineland
Adaptive Behavior Scales (VABS), a structured
interview designed to assess domains of adaptive
functioning (Sparrow, Balla, & Cicchetti, 1984).
Studies confirming the reliability and validity of the
VABS have solidified this measure as one of the most
widely used assessments of adaptive behavior (Sparrow & Cicchetti, 1985). Data from the Communication, Daily Living Skills, and Socialization scales
were included in the analyses for the current study.
The Communication Domain is comprised of three
sub-domains: Receptive, Expressive, and Written
Language. The Daily Living Skills scale includes the
Personal, Domestic, and Community sub-domains.
The Socialization scale is comprised of the Interpersonal, Play & Leisure, and Coping Skills subdomains.
Maladaptive Behavior
Three self-report questionnaires were administered to the primary caregivers of the children in our
study. First, parents completed the Conners Parent
Rating Scale (CPRS; Conners, 1989), a 48-item
measure designed to assess patterns of behavior
problems in children. The caregiver’s responses yield
T-scores with a mean of 50 and standard deviation of
10 on six subscales: Conduct Problems, Learning
Problems, Psychosomatic, Anxiety, Impulsive, and a
Hyperactivity Index. The CPRS is a widely used
measure of behavioral and emotional functioning in
children, and reliability and validity have been welldocumented (Conners, Sitarenios, Parker, & Epstein,
1998).
Parents also were administered modified versions
of the Stereotypy Checklist (Bodfish et al., 1995) and
the Self-Injurious Behavior Checklist (Powell,
Bodfish, Parker, Crawford, & Lewis, 1996), two
measures assessing the presence of maladaptive
behaviors. The Stereotypy Checklist (SCL) is an
instrument that asks the caregiver to indicate from a
list of stereotypical behaviors those in which their
child engages. On the Self-Injurious Behavior
Checklist (SBCL), the parent is asked to review a
list of self-injurious behaviors (SIBs) and indicate
those that their child exhibits. The modified versions
of these scales, used in a prior study of individuals
with SMS (Dykens & Smith, 1998), include several
additional behaviors specific to SMS (e.g., selfhugging, object insertion). An additional subscale
was added to each of these measures to assess the
severity of the behaviors. This subscale was structured as a 5-point Likert scale, and the parent was
asked to indicate how much each behavior interfered
with the child’s daily functioning (0=no interference
to 4=extreme interference). The versions of these
measures used in our study included 36 behaviors on
the SCL, and 11 behaviors on the SBCL. Data from
fifteen families were included in analyses, since these
measures were finalized following the assessments
conducted with the first four families enrolled on the
study. For all parent measures, if more than one
caregiver was present during the assessment, the
parent who typically spent the most time with the
child was asked to complete the questionnaires and
participate in the VABS interview.
To assess autistic-like behaviors, the Childhood
Autism Rating Scale (CARS; Schopler, Reichler, &
Renner, 1999) was completed by the examiner after
each evaluation. For this scale, the examiner rates the
child on 15 maladaptive behavioral items relevant to
autism, such as relating to people, imitation, activity
level, and nonverbal communication. Items are
scored on a scale ranging from 1 (age-appropriate;
no abnormality) to 4 (severely abnormal), and a total
score is calculated by summing item responses.
Possible total scores, which range from 15 to 60,
correspond to three categories: Non-autistic (15.0–
29.5), Mildly to Moderately Autistic (30.0–36.5), and
Severely Autistic (37.0–60.0).
Statistical Analyses
Non-parametric statistics were used since the
scores obtained by our patient sample on measures of
interest were not normally distributed. The Wilcoxon
rank-sum test was used to compare differences
between VABS subscales and between CPRS subscales. Spearman correlation coefficients were examined to assess the relationship between scores on
measures of adaptive and maladaptive behavior, and
cognitive functioning, and to examine whether agerelated differences were present on any of the
variables of interest. To assess for gender differences,
the Wilcoxon rank-sum test or Chi-square tests of
Behavior in Smith-Magenis Syndrome
independence were employed depending on whether
the dependent variable was continuous or categorical.
For analyses involving sub-domains on the VABS,
age-equivalent scores were transformed to standard
scores to allow for comparisons with other standardized scores (e.g., IQ). In addition, scores on the SB-IV
were transformed to have a standard deviation of 15
in order to be consistent with other measures (BSIDII, VABS). Due to the number of analyses performed,
alpha was set at .01.
RESULTS
Cognitive Functioning
Of the 19 children in our study, one child
demonstrated significant behavioral difficulties during the testing session and a valid assessment of
cognitive functioning was not obtained. Thus, IQ
scores are reported for the 18 remaining children. A
vast majority of children were functioning considerably below average (mean IQ score=62.5±14.4),
with IQ scores ranging from 39 to 84. Based on
classifications outlined in the Diagnostic and Statistical Manual of Mental Disorders—Fourth Edition
(DSM-IV; American Psychiatric Association, 1994),
67% (n=12) of children in our sample met criteria for
either mild (n=6) or moderate (n=6) mental retardation. An additional 28% (n=5) fell in the Borderline range of intellectual functioning, and 6% (n=1)
scored in the Low Average range of cognitive ability.
There were no significant gender differences or
age-related effects with respect to IQ (ps>.01).
Adaptive Behavior
Based on parent interviews with the VABS,
children in our sample were functioning significantly
below average in all areas of adaptive functioning.
Mean scores on the Socialization subscale
(mean=70.0±13.3) were significantly higher than
scores on the Communication (mean=62.5±15.8)
and Daily Living Skills (mean=54.9±13.5) subscales
(ps<.01). Communication scores were higher than
Daily Living Skills scores, but this difference did not
reach statistical significance (p>.01). No significant
gender differences were revealed on any of the VABS
domains (ps >.01). However, the child’s age was
inversely related to Daily Living Skills (r=).68,
p<.001). Thus, proficiency with activities of daily
living seemed to get worse in comparison to agerelated peers as chronological age increased.
An examination of standard scores based on
VABS sub-domain age equivalents provides a similar
picture as that revealed from the primary domains.
Children’s mean scores were well below average on
all sub-domains, and no gender or age-related differences were present (all ps >.01).
Maladaptive Behavior
Conner’s Parent Rating Scale
As shown in Table I, parent responses on the
CPRS indicated the presence of significant elevations,
defined as having a T-score greater than or equal to
70, on the Learning Problems (mean=81.4±13.1)
and Hyperactivity (mean=70.5±14.0) scales. These
subscale scores were significantly higher than the
remaining four subscales (ps<.01), and the mean
Learning Problems score was significantly higher
than the mean score on the Hyperactivity Index
(p<.001). Mean scores on the Impulsivity Scale were
not significantly higher than the Psychosomatic
scores (p>.01), but were significantly higher than
scores on the Anxiety and Conduct Problems scales
(ps<.01), although each of these four scales were
within normal limits.
The mean scores obtained by girls and boys on
each of the subscales of the CPRS are displayed in
Table I. Analyses revealed a significant gender difference on the Impulsivity subscale. Parent ratings of
impulsive behavior for girls (mean=65.0±13.0) were
significantly higher than ratings for boys
(mean=50.5±10.1; p<.01). The unexpectedness of
this finding led us to wonder if the result was an
artifact of the standardization process. That is,
perhaps girls with SMS are not actually exhibiting
more impulsiveness than boys, but transforming the
Table I. Mean T-scores on the Conners Parent Rating Scale
(CPRS)
CPRS subscalea
Conduct
Learningb
Psychosomatic
Impulsivec
Anxiety
Hyperactivityb
a
Mean (SD)
Total sample
47.9
81.4
54.9
58.2
48.1
70.5
(10.4)
(13.1)
(14.3)
(13.6)
(7.1)
(14.0)
Mean (SD)
Boys
Mean (SD)
Girls
42.9
81.2
51.7
50.5
47.2
63.0
52.5
81.6
56.4
65.0
48.8
77.3
(5.2)
(14.5)
(9.5)
(10.1)
(7.6)
(9.3)
(12.0)
(12.5)
(18.1)
(13.0)
(6.8)
(14.4)
CPRS t-scores have a mean of 50 and standard deviation of 10.
Subscale mean fell in the clinically elevated range.
c
Difference between boys and girls significant at .01 level.
b
Martin, Wolters, and Smith
raw scores to standard scores may have given the
impression of a more impaired level of impulsivity in
girls, given the base rates of these behaviors in nondisordered children. To explore this further, we
examined the raw scores of the girls and boys in
our sample. These raw scores were consistent with the
previous finding based on the standard scores. Raw
scores on impulsivity also were higher for girls
(mean=7.9±3.4) than boys (mean=4.0±2.3).
Although the tendency for girls to score higher
on the Hyperactivity scale emerged as a nonsignificant trend (p=.015), no other gender differences were
demonstrated on the remaining CPRS subscales at
the .01 level. None of the subscales were related to the
chronological age of the child (ps>.01).
category: ‘‘stares closely at objects or hands.’’ Among
the most frequently reported stereotypic behaviors
were teeth grinding (87%), inserting hands in mouth
(87%), and inserting objects in mouth (80%). On the
5-point Likert scale described earlier, parents rated
the extent to which present stereotypical behaviors
interfered with their child’s life. Of these most
frequent behaviors, inserting hands and inserting
objects in mouth both were rated as interfering at
least moderately in the child’s life. The remaining
stereotypic behaviors reported were described as
interfering with the child’s functioning only minimally, if at all.
Stereotypy Checklist
Results of the SBCL are summarized in Table III.
Of the 11 behaviors listed, the number of SIBs reported
ranged from 2 to 9 (mean=5.4). The most frequently
reported SIBs included hitting oneself (93%) and biting
oneself (80%). Mean parent ratings for both of these
behaviors indicated that they interfered mildly in the
child’s life. One behavior’s mean rating suggested at
least a moderate level of interference: ‘‘pulls out finger
or toe nails,’’ and this behavior was demonstrated by
13% (n=2) of the children in our sample. All other
behaviors on the SBCL were described as interfering to
a mild extent in the child’s life.
Chi-square tests of independence were utilized
for determining if any gender differences were present
with respect to individual stereotypic and self-injurious behaviors. Results of these analyses indicated
that boys engaged in repetitive shouting significantly
Of the 36 items on the SCL, the number of
reported stereotypic behaviors ranged from 6 to 22
(mean=13.2). The percentages of children who
exhibited each stereotypic behavior are reported in
Table II. For purposes of simplicity and space in the
table, items assessing similar aspects of a particular
behavior pattern were combined to create composite
items. For example, ‘‘stares closely at objects’’ was
combined with ‘‘stares closely at hands’’ to form one
Table II. Number of Children Exhibiting Stereotypic Behaviors
(n=15)
Behavior
N
%
Grinds teeth
Inserts hands in mouth
Inserts objects into mouth
Covers ears or eyes
Hugs/squeezes upper body
Turns book pages repetitively
Walks on tip-toes
Flaps, waves, or claps hands
Purposely drops or throws objects
Taps or rubs objects or body
Rocks or sways back and forth
Stares closely at objects or hands
Whirls, turns in circles
Jumps repetitively
Shouts repetitively (when not upset)
Smells, sniffs objects
Rolls, tilts, or turns head
Immediate or delayed echolalia
Breathes forcefully
Wiggles or flicks fingers
Maintains set body posture
13
13
12
10
9
9
9
9
9
8
8
8
7
6
5
5
5
4
4
3
3
87
87
80
67
60
60
60
60
60
53
53
53
47
40
33
33
33
27
27
20
20
Self-Injurious Behavior Checklist
Table III. Number of Children Exhibiting Self-injurious Behaviors
(n=15)
Behavior
N
%
Hits self
Bites self
Hits self against
surface or object
Inserts fingers or
objects into other body
openings (besides mouth)
Pulls hair or skin
Rubs or scratches self
Pulls hair out
Hits self with object
Pokes self in eye
Pulls out finger or toe nails
Pulls out teeth
14
12
8
93
80
53
7
47
6
5
4
4
3
2
1
40
33
27
27
20
13
7
Behavior in Smith-Magenis Syndrome
more than girls (v2=7.27, p=.007). Other nonsignificant patterns revealed the tendencies for girls to
engage in staring closely at objects (v2=6.35,
p=.012) and pulling out their hair (v2=6.23,
p=.013) more than boys.
Childhood Autism Rating Scale
With respect to the evaluator’s ratings on the
CARS, children obtained a mean total score of
31.3±4.3, indicating that these children’s behavioral
profiles fall at the low end of the Mild classification of
autism. As stated previously, the Mild to Moderately
Autistic category ranges from 30 to 36.5. Total scores
obtained by our sample of children ranged from 24 to
37, and no gender differences or age-related differences were present (ps>.01).
Relationship Between Adaptive Behavior, Maladaptive
Behavior, and Cognitive Functioning
from IQ scores (ps>.01). Results of Spearman correlation analyses assessing the relationship between
cognitive and adaptive functioning are shown in
Table IV. As can be seen in the table, Socialization
scores were significantly correlated with IQ (p<.01).
An analysis of Socialization sub-domains revealed
that scores on the Interpersonal Skills and the Play
and Leisure subscales were positively correlated with
IQ (ps <.01), and the relationship between IQ and the
Coping Skills sub-domain approached significance
(p<.01). Scores on the global Communication
domain were significantly related to IQ (p<.01), and
the sub-domains assessing receptive and expressive
communication were also positively related to IQ
(ps<.01). The Written Language sub-domain was not
associated with IQ (p>.01). IQ scores were not
related to the Daily Living Skills domain scores, or
to any of the three sub-domains (Personal, Domestic,
and Community; ps>.01).
Adaptive Behavior and Cognitive Function
Adaptive and Maladaptive Behavior
As shown in Fig. 1, children’s scores on the
Socialization scale were significantly higher than their
IQ score (p<.01), while Communication and Daily
Living Skills scores were not significantly different
No relationships between adaptive and maladaptive behavior were evident. Global adaptive
behavior domain scores on the VABS were not
related to behavior subscales on the CPRS, or to the
90
80
70
60
50
40
30
20
IQ
Communication
Daily Living Skills
Socialization
Fig. 1. Mean standard scores on the Communication, Daily Living Skills, and Socialization domains of the Vineland
Adaptive Behavior Scales and IQ scores.
Martin, Wolters, and Smith
Table IV. Spearman Correlations Between VABS Domains
Sub-domains and IQ
Domain/Sub-domain
Communication
Receptive
Expressive
Written
Daily Living Skills
Personal
Domestic
Community
Socialization
Interpersonal
Play & Leisure
Coping Skills
IQ
.62*
.87**
.60*
.21
.44
.35
.57
.57
.63*
.63*
.64*
.62
Note. VABS=Vineland Adaptive Behavior Scales.
*p<.01, **p<.001.
number or severity of stereotypic or self-injurious
behaviors reported (ps>.01). Analyses of VABS subdomains also showed no significant relationships with
CPRS subscales, or the number and severity of
behaviors reported on the SCL or SBCL (ps>.01).
Total scores on the CARS were unrelated to scores
on the three VABS subscales (ps>.01).
Cognitive Function and Maladaptive Behavior
There were no significant relationships between
cognitive functioning and maladaptive behavior.
Problem behaviors as indicated on the CPRS were
not associated with cognitive abilities (ps>.01).
Similarly, the number and severity of maladaptive
behaviors reported by parents on the SCL and SBCL
were unrelated to the child’s level of cognitive
functioning (ps >.01). Finally, total scores on the
CARS were unrelated to IQ scores (p>.01).
DISCUSSION
This study is the first to provide a thorough
description of adaptive and maladaptive behavior
based on objective, validated assessment techniques,
and their relationship to cognitive functioning specifically among children with SMS. With respect to
cognitive functioning, the majority of children in our
sample (67%) met criteria for mild or moderate levels
of mental retardation (MR), and the range of scores
was wide, from severely delayed to the low end of the
average range in one child. Compared to another
report in the literature (Udwin et al., 2001) in which
all child participants were described as mentally
retarded, six of the children in our study scored
above the cut-off for MR on an objective measure of
intellectual abilities. There are several differences
between the groups of children assessed in these two
studies. The children in Udwin’s study were somewhat older than ours, ranging in age from 6 to 16
years with a mean age of 9.3. Also, while Udwin’s
study reports results from the Wechsler Intelligence
Scale for Children—Third Edition (WISC-III;
Wechsler, 1991), our children were tested with the
BSID-II and SB-IV due to their younger age.
Adaptive functioning among our sample of
children with SMS was delayed in all areas. Socialization skills proved to be an area of relative strength,
emerging as significantly more developed than daily
living skills and communication skills. This is in
contrast to results reported by Dykens et al. (1997),
who found no differences between the three aforementioned areas of adaptive functioning. However,
Dykens’ study included individuals ranging in age
from 14 to 51, so the extent to which age-related
changes may have existed in her sample remains
unclear. Age was significantly related to daily living
skills in our study. Specifically, as the age of the child
increased, scores on the daily living skills domain
decreased. Thus, acquisition of daily living skills may
plateau in children with SMS while peers without
SMS continue to gain new skills.
With respect to the relationship between adaptive behavior and cognitive functioning, daily living
skills and adaptive communication abilities were
consistent with cognitive test results, while socialization skills were significantly higher than IQ scores.
This finding points to interesting comparisons
between children with SMS and other developmentally delayed populations. Specifically, socialization
in autistic children tends to be the area of most
notable delay compared to other adaptive behavior
areas, and is often significantly lower than IQ
(Freeman et al., 1988). In contrast, children with
SMS often are described as friendly, affectionate, and
outgoing, much like the characteristics of children
with Down Syndrome (Loveland & Kelley, 1991). In
children with Williams Syndrome, socialization skills
have been found to be significantly higher than daily
living skills, and yet consistent with IQ (Greer et al.,
1997).
Scores from the Communication and Socialization scales of the VABS were significantly related to
IQ, while Daily Living Skills scores were not. To date,
no other published studies have reported correlations
Behavior in Smith-Magenis Syndrome
between objective measures of cognitive and adaptive
functioning among the SMS population. Investigations of children with autism have reported inconsistent findings with respect to the nature of the
relationship between these variables. While some
studies of autistic children have found that all three
domains of the Vineland (Communication, Socialization, and Daily Living Skills) were significantly
correlated with IQ (Carpentieri & Morgan, 1996;
Freeman et al., 1988), others have suggested that the
relationship depends upon the ability level of the child
(Freeman et al., 1991; Liss et al., 2001). For example,
significant correlations between scores on the WISCR and the three Vineland domains were obtained in a
study of 53 children and adolescents with autism
(Freeman et al., 1991). However, for a subgroup of 13
participants with higher IQ scores (mean IQ=97.8),
only the Communication domain was significantly
associated with cognitive level. It is likely that the
relationship between cognitive and adaptive functioning differs across populations, so further studies with
children with SMS are needed in order to more fully
explore these variables and the implications of how
they interact.
Of the few studies of children with SMS that
include data on adaptive functioning as assessed by
the VABS, none have examined the various subdomains of the scales. Our study found that IQ was
correlated with several sub-domains of adaptive functioning within the Communication and Socialization
scales, but was not related to any of the Daily Living
Skills sub-domains. Regarding the Communication
scale, receptive and expressive communication were
related to cognitive functioning in our study, but
written communication was not. Items on the Written
Communication sub-domain are geared toward
children beginning at age 5, while the suggested basal
age for the Receptive and Expressive sub-domains is
less than 1 year. Given the typical ability level of our
patient sample, many children reached their ceiling
on the Written Communication sub-domain prior to
or close to items at the 5-year age level. Thus, this
sub-domain may not be developmentally appropriate
for our sample and interpretations based on this
subscale are limited.
Within the Socialization scale, scores on the
Interpersonal Relations and the Play and Leisure subdomains were correlated with IQ, while scores on the
Coping Skills sub-domain were unrelated to IQ.
Many items on the Coping subscale are related to
the child’s ability to inhibit inappropriate behavioral
impulses and follow rules. Obviously, the maladaptive
behaviors present among children with SMS would
interfere with a child’s ability to score high on the
Coping Skills subscale.
Maladaptive behaviors proved to be a notable
problem among the children in our study. Results
from the CPRS revealed significant learning problems, which is consistent with test results from the
standardized IQ assessments. Hyperactivity was
another area of concern indicated by the CPRS,
and this validates other published reports characterizing the behavioral phenotype of children with SMS
(Dykens & Smith, 1998). Additional maladaptive
behaviors commonly reported by parents of children
in our study included teeth grinding, insertion of
hands or objects into their mouths or other body
openings, and self-injurious behaviors in the form of
hitting, scratching, and biting.
In another assessment of self-injurious behaviors
among children with SMS, Finucane and colleagues
(2001) found that 86% engaged in self-biting and 33%
in hair-pulling, rates that are similar to our sample.
However, 27% of the children in Finucane’s study
engaged in pulling out fingernails or toenails, compared with only 13% of the children in our sample. In
general, the frequencies of SIBs reported in both
studies suggest that these behaviors are not an
uncommon occurrence among children with SMS.
Examination of stereotypic and self-injurious
behaviors indicated that several of these behaviors,
particularly those involving the child inserting their
hands or other foreign objects into their mouth,
interfered at least moderately with the child’s daily
functioning. However, the majority of behaviors,
such as hitting and biting oneself, were described by
parents as causing only minimal interference. Thus,
these data suggest that most children with SMS do
not significantly hurt themselves or cause considerable disruption when engaging in these behaviors.
The fact that parents did not indicate more of a
disruption also may suggest that they have found
moderately successful methods for dealing with their
child’s stereotypic and self-injurious behaviors,
thereby decreasing the level of interference that
would otherwise be induced by such behaviors.
Despite the fact that children with SMS share a
number of behaviors with autistic children (selfinjurious behavior, delayed verbal language), results
of the CARS emphasized the apparent differences
between the two disorders, such as the contrast in
socialization skills discussed previously. Children in
our study typically fell at the low end of the Mildly
Autistic classification category, suggesting that the
Martin, Wolters, and Smith
general behavioral presentations are not as similar as
some might think. Thus, it is essential to consider a
diagnosis of SMS and a genetic assessment in
children who present with SIBs and lack of verbal
language, especially if they have adequate social
skills. Nonetheless, it is important to note that our
study lacks an actual comparison group of autistic
children. Any conclusions made regarding similarities
and differences between the SMS and autistic populations should be interpreted with caution. Further
studies are needed that directly compare children
with SMS and Autistic Disorder.
The presence of maladaptive behaviors, as
assessed by the CPRS, SCL, SBCL, and CARS,
was independent of both adaptive functioning and
cognitive functioning in this group of children with
SMS. The lack of relationship between cognitive
functioning and maladaptive behavior is in accordance with results in the autism literature (Freeman
et al., 1991), although a prior report on children with
SMS suggested that the prevalence of SIBs was
positively related to intellectual functioning (Finucane et al., 2001). The fact that Finucane’s study
assessed cognitive impairment via parent report
through a telephone interview while our study used
objective test scores may be a contributing factor to
this difference. A lack of a significant relationship
between adaptive and maladaptive behavior is not a
unique finding among children with developmental
disabilities. A review of other populations reveals
that adaptive and maladaptive behavior have been
found to be unrelated to each other in children with
Fragile X and Down Syndrome (Fisch et al., 1999),
both of which are populations with cognitive and
developmental delays.
Results of our exploratory analyses examining
gender differences in our sample revealed that girls
were described as more impulsive than boys. This is
an interesting finding given the historical tendency for
boys to display more impulsivity than girls, both in
normal (Cote, Tremblay, Nagin, Zoccolillo, & Vitaro, 2002) and Attention Deficit Hyperactivity Disorder (Newcorn et al., 2001) populations. The only
other significant gender difference to emerge in terms
of individual maladaptive behaviors in our study
suggested that boys with SMS engage in more
repetitive shouting than girls. While little is known
about variations in patterns of behavior among girls
vs. boys in the SMS population, there is preliminary
evidence based on animal models from a recent study
examining behavior in mice that were genetically
engineered to have the p11.2 deletion on chromosome
17 (Walz et al., 2004). Results indicated that male
SMS mice exhibited hypoactivity compared with
wild-type mice, but this difference in activity level
was not seen in female mice with the SMS deletion. It
is premature to draw conclusions about implications
for humans with SMS, but these results would be
consistent with our findings of girls being more
impulsive (and hyperactive at a non-significant level)
than boys. Studies comparing gender differences in
children with SMS are sorely needed. In fact, in a
review article by Thompson, Caruso, and Ellerbeck
(2003), the authors perceptively make the point that
an astoundingly small proportion of studies of
individuals with developmental disabilities consider
possible gender differences in their samples. Thus,
despite the findings presented here, there is a clear
need for more research in this area before definitive
conclusions can be drawn regarding any systematic
gender differences in the SMS population.
An inherent limitation of descriptive research lies
in the lack of a control group. As previously noted, the
purpose of this study was to describe patterns of
adaptive and maladaptive behavior among children
participating in a natural history study of SMS. Our
findings should be viewed in this context. Future
research goals need to incorporate comparison groups
comprised of other developmentally delayed populations as well as non-disordered individuals in order to
expand our understanding of the specific nature of
SMS. Another limitation of this study was the somewhat small sample size, although it was larger than
many that have been published on this population.
Systematic objective longitudinal research to
examine the way that cognitive functioning and
adaptive/maladaptive behavior changes over time is
critically needed. Data from the current study is part
of a longitudinal research project that aims to accomplish this goal. Smith-Magenis Syndrome remains a
relatively under-diagnosed disorder, and there is much
about this syndrome we have yet to fully understand.
By gaining a more complete picture of the pattern of
strengths and weaknesses in these children, we can
begin to design therapeutic interventions in an effort
to help them reach their full potential.
ACKNOWLEDGMENTS
This research was supported by the Intramural
Research Program of the National Institutes of
Health, the HIV and AIDS Malignancy Branch of
the National Cancer Institute through federal
Behavior in Smith-Magenis Syndrome
contracts 71004-09 and N01-SC-07006 with the
Medical Illness Counseling Center, and a Bench-toBedside award from the Clinical Center at the NIH to
the Medical Genetics Branch of the National Human
Genetics Research Institute. The authors would like
to express their sincere appreciation to the families
who agreed to participate in this research. We also
extend our gratitude to members of the SMS
Research Team, especially Mary Anne Tamula,
M.A., Donna Krasnewich, M.D., Suzan Parada,
R.N., and Rebecca Morse, B.A.
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